1. Field of the Invention
The present invention relates to a laser irradiation method for laser treatment performed by irradiating a treatment part or site such as an affected part with a treatment laser beam and a laser treatment apparatus used for practicing the irradiation method.
2. Description of Related Art
Conventionally, there have been known laser treatment apparatus for performing depilation, wrinkle removal, and birthmark removal, etc. by irradiating a skin surrounding hair follicles or a skin having wrinkles or birthmarks with a treatment laser beam (simply referred to as a treatment beam hereinafter). For example, in laser depilation treatment, a treatment beam is irradiated to a skin surrounding hair follicles, and resultant heat is radiated to the hair roots and then cauterizes them, thus depilating the hairs. Known as an irradiation method of the treatment beam is the method of determining in advance an area (its shape, size, and others) to be irradiated in response to one irradiation command signal and then irradiating the treatment beam to the predetermined area while scanning so that beam spots (spot positions) of the treatment beam are arranged within the irradiation area.
However, it has been determined such that scanning the beam spots is made by causing the treatment beam to sequentially scan the irradiation area from an end spot in a first scanning line to a next, as shown in FIG. 5, and the scanning is repeated on a second scanning line immediately adjacent to the first scanning line, and then to a third scanning line. At this time, without considering the effects of a heat damping time in an immediately preceding irradiated spot, the treatment beam is irradiated to a next (immediately adjacent) spot, which is liable to cause the thermal damage to the skin.
It is to be noted that the heat damping time is defined as follows: when a treatment beam is irradiated to a target, the distribution of temperatures in a zone centered on the target is observed as a Gaussian distribution with the width which depends on the diameter of the zone; in relation to the Gaussian distribution, the heat damping time is interpreted as the time required until the center temperature of the Gaussian distribution decreases to 50% thereof.
For solving such the problem, there has been proposed a method of scanning the treatment beam over the irradiation area so that the beam spots of the treatment beam are arranged at random as shown in FIG. 11. However, there is no guarantee that the beam spots continuously irradiated will not be immediately adjacent to the immediately preceding irradiated spots. This method can predetermine a plurality of types of an irradiation area such as its shape, size and others, and memorize beforehand a scanning pattern (a scanning sequence) determined such that the beam spots irradiated continuously are arranged without becoming immediately adjacent to each other. It however needs complicated operations to beforehand determine scanning patterns for every irradiation area. When a new irradiation area is set, furthermore, determination of a scanning pattern corresponding to the area also requires complicated operations.
Furthermore, in the conventional method of scanning beam spots, the treatment beam is irradiated to the skin even while the treatment beam is shifting from a beam spot to another. This would apply undesired heat energy to an affected part of the skin and also cause wasted power consumption.
The present invention has been made in view of the above circumstances and has an object to overcome the above problems and to provide a laser irradiation method for laser treatment enabling suppression of the thermal damage to a skin irradiated with a treatment laser beam, and a laser treatment apparatus used for practicing the method.
Another object of the present invention is providing a laser irradiation method for laser treatment enabling easy determination of a scanning sequence of beam spots without requiring complicated operations, and a laser treatment apparatus used for practicing the method.
Furthermore, the present invention has another object of providing a laser irradiation method for laser treatment capable of performing laser irradiation in an appropriate, efficient manner, and a laser treatment apparatus used for carrying out the method.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the purpose of the invention, there is provided a laser irradiation method for laser treatment performed by irradiating a treatment part of a patient with a treatment laser beam, the method including the steps of: a. setting a shape and size of an irradiation area to be irradiated with the laser beam; b. determining a scanning sequence of beam spots based on the shape and size of the irradiation area set in the setting step, a spot diameter of the laser beam, and a predetermined rule; and c. performing laser irradiation to the beam spots within the irradiation area in accordance with the scanning sequence determined in the determining step; wherein the predetermined rule is a rule that the beam spots continuously irradiated with the laser beam become nonadjacent and scanning lines continuously irradiated become nonadjacent.
According to another aspect of the present invention, there is provided a laser treatment apparatus for performing treatment for a treatment part of a patient by irradiating the part with a treatment laser beam, the apparatus including: a light delivery optical system provided with a laser source for emitting a treatment laser beam, for forming the laser beam emitted from the laser source into a spot beam and delivering the beam to the treatment part to be irradiated; scanning means disposed in the light delivery optical system, for scanning the laser beam onto beam spots within an irradiation area having a predetermined shape and size; determining means for determining a scanning sequence of the beam spots to be scanned by the scanning means based on a shape and size of an irradiation area, a spot diameter of the laser beam, and a predetermined rule; and scanning control means for controlling the scanning means to perform laser irradiation based on the determined scanning sequence; wherein the predetermined rule is a rule that beam spots continuously irradiated with the laser beam become nonadjacent and scanning lines continuously irradiated become nonadjacent.
Furthermore, according to another aspect of the present invention, there is provided a laser treatment apparatus for performing treatment for a treatment part of a patient by irradiating the part with a treatment laser beam, the apparatus including: a light delivery optical system provided with a laser source, for emitting a treatment laser beam, for forming the laser beam emitted from the laser source into a spot beam and delivering the beam to the treatment part to be irradiated; scanning means disposed in the light delivery optical system, for scanning the laser beam onto beam spots within an irradiation area having a predetermined shape and size; scanning control means for controlling the scanning means to perform laser irradiation based on a predetermined scanning sequence; and irradiation control means for controlling the laser irradiation in correspondence with shifting of the laser beam from a beam spot to a next by the scanning means.